1. Field of the Invention
The present invention relates to a method for respirating of patients, whereby use is made of an apparatus which is provided with means for circulating a gas in one direction in a line or conduit system, with means for varying the pressure in the line system in accordance with a certain respirating pattern, with means for measuring the flow of the gas and the composition of the gas, whilst the line system is provided with connecting means for the patient and with one or more supplies for the various components of the respiratory gas, whereby the line system further is provided with a connecting means to a discharge line that is provided with a closing device for the discharge out of the line system of gas, whilst in the line system, as seen in the direction of the circulation of the gas, behind the connecting means to the discharge line a second closing means is provided.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 And 37 CFR 1.98
Such a method is known.
With the known method it is possible to switch from an open system, in which the patient again and again breathes in fresh breathing gas and the breathing gas exhaled by the patient is discharged completely out of the line system (non-rebreathing), to a half closed system, in which a part of the breathing gas exhaled by the patient is circulated once again and a part is discharged outside (some form of rebreathing).
The known method in the closed system has the drawback, that the “washing in” of the patient, that is to say the intake of anesthetic gas by the patient, takes a relatively long time. The patient among other things has nitrogen in his lungs, which has to be removed before the anesthetic can be started. To that end the patient is administered 100% oxygen until practically all nitrogen has been ventilated out of the lungs (the “washing” of the lungs with oxygen). In the closed system this takes much time, because each time the oxygen is inhaled together with a part of the gas that is already present. After the washing of the lungs of the patient with oxygen an anesthetic gas, here the carrier gas, such as xenon, is supplied, of which the patient takes in and exhales again a part. The amount of oxygen and xenon that is taken in is each time compensated with only xenon until the desired concentration of oxygen and the desired concentration of xenon is obtained in the breathing gas, which is the case only after a long time. The anesthetic or sedation here has to take place by other means.
In the half closed system a surplus of xenon, together with oxygen or not, is allowed to flow into the line system, by which the system gets to be overfilled. This is compensated by a “pop-off” system, in which a part of the gas in the system is discharged outside. Because of this the concentration of xenon increases. The more gas is supplied the faster the patient is washed in. This however leads to a substantial loss of gas.
It is an object of the invention to obviate this drawback of the known method.